Problem: Evaluate the following expression when $c = 6$ and $d = 6$. $7$ $c$ $ + 9$ $d$ $ + 6$
Answer: Substitute $6$ for ${c}$ and $6$ for ${d}$ $ = 7{(6)} + 9{(6)} + 6 $ $ = 42 + 54 + 6 $ $ = 102$